Curious but interesting
I have been measuring and comparing the spare Nordie/RC barrel and piston I brought back with me with the ex 72degrees Nordie hillclimb Frigioli big bore barrel.
Nobody, including Frigioli, could remember, or tell me the head gasket thickness, so I assumed it must be the same 1.4/1.5mm compressed thickness of the standard gasket.
Putting the 2 barrels side by side the Nordie/RC base to head face is longer at 75.5mm than the Frigioli 74.2mm, implying that the Frigioli gasket would be 2.8mm thickness to maintain the timing belt relationship between the crank pulley and cam pulleys, alter this and you are playing with vernier pulleys to get the correct cam timing.
We know that 72degrees had gasket leaking issues with compression gasses pressurising the cooling system, I suspect this cannot have been helped by having such a thick gasket, the best leak-less joint is not to have one, or have lapped metal to metal faces as used in historic Napier engines, or gas filled sealing rings as used by NSU in some of their 1970’s car engines, never a gasket failure.
Frigioli machined a raised 0.5mm high step around the edge of the bore to increase sealing pressure onto the gasket at the head face, which implies they were trying to cure a known problem??
So gentlemen what are your thoughts on this, stay with the thick gasket, known to be problematic?
Increase the base thickness gasket and use a reduced thickness head gasket?
Increase the base thickness gasket more and go metal to metal using a fluorocarbon O ring seal and high temperature silicon sealer around the water passages?